Machines such as, for example, dozers, loaders, excavators, motor graders, and other types of heavy machinery typically include a power source linked to a power conversion unit. Such a configuration is used for transmitting torque from the power source to one or more axle assemblies operatively connected to one or more traction devices for movement of the vehicle over one or more supporting surfaces (e.g., the ground). Torque applied at the axle assemblies may result in rotational motion of components associated with the axle assemblies and, in turn, the traction devices. Thus, the machine may be put in motion based on available friction between the traction devices and the supporting surface, among other things.
The transmission of high torques from the power conversion unit to the axle assemblies may result in strain and possible damage to components of the axle assemblies, particularly where friction between the traction devices and supporting surface is high. Such strain and damage can eventually or immediately lead to failure of components associated with the axle assemblies (e.g., gear bending, gear pitting, roller bearing damage, ball bearing damage, etc.) and removal of the machine from operation for repairs. Therefore, it may be beneficial to implement systems and methods for determining current torque applied at an axle assembly and limiting such torque to a preferred torque value below which strain and damage may occur.
Previous systems and methods have been used to limit a transmission output torque for machines. Such systems can include position sensors configured to determine a position of an implement and adjusting engine speed to control engine torque output. For example, U.S. Pat. No. 6,234,254 (the '254 patent) issued to Dietz et al. on May 22, 2001, describes an apparatus for controlling the torque associated with a power train of a machine having an implement. A plurality of position sensors sense the position of the work implement and produce respective position signals. In addition, pressure sensors associated with implement system hydraulic cylinders may sense pressures in the cylinders and provide related information to the controller. This position information is processed by a controller to determine a “dig trigger” (i.e., is the implement in operation) and the engine speed is modified to control the power train torque such that efficient operation of the implement may be accomplished.
Although the system and method of the '254 patent may provide for controlling of power train torque based on implement position and/or pressure, it is targeted toward improving the work cycle of the implement. As such, it is limited to operation based on the dig trigger and implement pump pressures to optimize lift performance of the implement. In other words, there is no consideration for torques applied to an axle assembly or for limiting stress associated with axle assembly components, and therefore, such stress and potential damage may still occur.
The present disclosure is directed at overcoming one or more of the problems or disadvantages in the prior art control systems.